1. Field of the Invention
The present invention relates to a ceramic electronic component and a method for manufacturing the same. In particular, the present invention relates to the structure of a terminal electrode included in a ceramic electronic component and a method for manufacturing the same.
2. Description of the Related Art
Examples of known ceramic electronic components include laminated ceramic electronic components, e.g., laminated ceramic capacitors. FIG. 3 is a sectional view showing a conventional laminated ceramic capacitor 1.
The laminated ceramic capacitor 1 includes an electronic component main body 2 made of ceramic. The electronic component main body 2 has two opposed end surfaces 3 and 4 and a side surface 5 extending between the end surfaces 3 and 4. The electronic component main body 2 includes a plurality of laminated dielectric ceramic layers 6 and internal electrodes 7 and 8 disposed along interfaces between the dielectric ceramic layers 6.
Furthermore, the laminated ceramic capacitor 1 includes terminal electrodes 9 and 10 arranged so as to cover the end surfaces 3 and 4, respectively, of the electronic component main body 2 and extend to a portion of the side surface 5 from each of the end surfaces 3 and 4. The internal electrodes 7 are electrically connected to one terminal electrode 9, and the internal electrodes 8 are electrically connected to the other terminal electrode 10. The internal electrodes 7 and the internal electrodes 8 are alternately arranged in the lamination direction.
The terminal electrodes 9 and 10 are not shown in detail in FIG. 3. However, typically, the terminal electrodes 9 and 10 include thick film layers formed by applying an electrically conductive metal paste to predetermined regions of the surfaces of the electronic component main body 2, followed by baking and plating layers formed by subjecting the thick film layers to a plating treatment.
In use, as shown in FIG. 3, the laminated ceramic capacitor 1 is mounted on a wiring substrate 11. More specifically, solder fillets 14 and 15 are formed by soldering on electrically conductive lands 12 and 13 disposed on the wiring substrate 11, and the terminal electrodes 9 and 10 are electrically connected through the solder fillets 14 and 15, respectively.
During the formation of the thick film layers of the terminal electrodes 9 and 10, since a glass component included in the electrically conductive metal paste used to form the thick film layers reacts with the ceramic on the electronic component main body 2 side, a fragile reaction layer is formed at the interface between the thick film layer and the electronic component main body 2. Consequently, if a relatively large stress is applied to the thick film layer, cracking may start at an end of the thick film layer in the electronic component main body 2. For example, if a stress caused by bending of the wiring substrate 11 is applied while the laminated ceramic capacitor 1 is mounted on the wiring substrate 11, as shown in FIG. 3, a crack may start at an end of the thick film layer toward the internal electrode 7 or 8. In some cases, a crack extends to the internal electrode 7 or 8 and, thereby, a short-circuit failure of the laminated ceramic capacitor 1 may occur.
To overcome these problems, an electrically conductive resin layer has been interposed between the thick film layer and the plating layer included in the terminal electrode (see, for example, Japanese Patent No. 3363369 and Japanese Unexamined Patent Application Publication No. 10-284343). According to the technology described in Japanese Patent No. 3363369 and Japanese Unexamined Patent Application Publication No. 10-284343, a stress from outside is absorbed by deformation of the electrically conductive resin layer, and thereby, cracking in the electronic component main body is prevented. In addition, when an excessive stress exceeds an acceptable range, peeling is likely to occur at the interface between the thick film layer and/or the plating layer and the electrically conductive resin layer, and thereby, the stress is reduced so as to prevent cracking in the electronic component main body.
In the terminal electrode having the above-described structure, when a stress that is greater than or equal to a predetermined value is applied, this stress is reduced by the interlayer peeling in the terminal electrode. Therefore, the bonding force at the interface in which such interlayer peeling is designed to occur is set at a relatively low value. Consequently, there is a problem in that the end of the terminal electrode is vulnerable to a tensile stress.
More specifically, when a plating layer is formed, a laminated ceramic capacitor is transported during production, or a laminated ceramic capacitor is mounted on a wiring substrate by soldering, the plating layer disposed on the electrically conductive resin layer applies a tensile stress to the electrically conductive resin layer, and this stress concentrates at an end of the plating layer, that is, the end of the electrically conductive resin layer. Consequently, the electrically conductive resin layer may be peeled at the end thereof. If the electrically conductive resin layer is peeled during mounting of the laminated ceramic capacitor, as described above, when a large stress is applied to the laminated ceramic capacitor afterward, the electrically conductive resin layer may not be able to provide sufficient stress reduction. As a result, cracking may occur in the laminated ceramic capacitor, and short-circuit failure may occur.